In wellbore drilling and completion, various components, including tubular elements (also typically referred to in the industry as “tubulars”) need to be connected to each other end-to-end or disconnected from each other, typically via corresponding threads at respective ends of the components. For example, in drilling, lengths of drillpipe need to be connected end-to-end in order to connect equipment at rig surface with a bottomhole assembly downhole.
In the past, manual tongs were used to make and break connection between tubulars and other components. This method was slow and inefficient and has been replaced by motorised tong units which can grip the tubulars in end-to-end orientation and apply torque, typically to one of the tubulars, to rotate the tubulars relative to one another in order to screw or unscrew the tubulars. Motorised tong units, however, had their own limitations including, for example, suitability for only relatively small ranges of pipe diameters. This drawback was overcome by providing the tongs with hydraulically actuated gripping jaws which were adjustable to grip pipes from wider ranges of diameters. However, this entailed difficulties in establishing and maintaining an adequate grip on the tubulars during rotation. A number of solutions have been proposed to address this problem.
For example, WO2004/076806 A1 (Maritime Hydraulics) describes a torque tong machine comprising a stationary tong unit for gripping one pipe and a rotating tong unit for gripping and rotating another pipe to connect it to the first pipe. The rotating tong unit has a fixed part and a rotary part mounted on the fixed part for gripping and rotating a pipe. The rotary part has gripping jaws which are movable into engagement with the pipe by respective hydraulic gripping cylinders arranged on the fixed part. Additionally, each gripping jaw includes a hydraulic holding cylinder mounted on the rotary part and the piston of the holding cylinder is operatively connected to the gripping jaw. When the gripping jaws are moved by the gripping cylinders, the pistons in the holding cylinders are moved out causing hydraulic fluid to flow into the holding cylinders. The fluid in the holding cylinders is controlled by a valve arrangement mounted on the rotary part and actuatable by a movable plate arranged on the fixed part and by a hydraulic master cylinder on the fixed part which controls a hydraulic slave cylinder on the rotary part. Once the desired pressure has been set on the holding cylinders, the valves are closed and the plate and the master cylinder are disconnected from the rotary part to enable rotation of the rotary part. Once the rotary unit starts rotating, it is not possible to control the pressure in the holding cylinders because the connection with the master cylinder on the fixed part has been interrupted.
A further disadvantage of the arrangement of WO2004/076806 A1, is that, like in many prior art arrangements, the stationary tong unit and the rotating tong unit are vertically spaced from one another to receive and rotate the tubulars in upright orientations. Thus, the tubulars to be connected, which are normally stored horizontally, need to be brought into upright positions before they can be received in and gripped by the tong units which is relatively cumbersome and can add significantly to the overall costs of connecting the tubulars.
Accordingly, the object of the present invention is to provide an improved tong apparatus and method for connecting tubulars which obviates and/or mitigates the above drawbacks.